Screen grid tube



Nov. 3, 1931. E. A. LEDERER SCREEN GRID TUBE Filed Dec. 28, 1928 '2 Sheets-Sheet l INVENTQR EAL EDE RER MAESRNE Nov. 3, 1931.

E. A. LEDERER 1,830,233 SCREEN GRID TUBE Filed Dec/28, 192s 2 Sheets-Sheet 2' INVENTOR E.A.L E12E R ATTORNEY Patented-Nov. a, 1931 v UNITED. STATES ANTON IiEDm-ol' ma: ORANGE, NEW

PATaNr- OFFICE nousn'nm 0012M. a conrona'rrorr or rmmvun Gain run: v a lication filed December as, me. semi no. man.

This invention relates to an electron discharge tube and more particularly to a tube of this nature employing a shieldin electrode struct the shielding electrode in the form of a closed box of suitable mesh or solid material having a transversely disposed partition of mesh or grid like material to separate the interior of the shielding electrode into two compartments. In one compartment the anode is located and in the other comprartment the control electrode is disposed. he partition is preferably of arched onsemi-cylmdrical form so that the control electrode and anode may be concentrically disposed. The cathode is positionedv to the side of the control electrode remote from the anode.

In order that the above and other features of the invention may be more fully understood reference will be hadto the accompany-.

ing drawings in which, I Fig. 1 is a section on the line I-' I.of Fig. 2 of one form of mount embodying my invention and employing an indirectly heated I cathode. 4

Fig. 2 is'a section on the line 11-11 of Fig. 1.

Fig. 3fis a perspective view of the shielding electrode.

Fig. 4 is a perspective view of a modified construction of tube.

Fig. 5 is a perspective view of the cathode and grid assembly employing a directly heated cathode.

Fig. 6 a sectional view of a still further modification taken on the line VI-VI of Fig. 7 and r 'Fig. 7 is a sectional view on the line VII- VII of F' in Figures 1, 2 and 3 comprises a cathode 10, control grid 11, anode 12 and screen grid 13. The cathode is of the indirectly heated type,

adapted to be heated by radiation from a separate heater element, energized b alternating current, and com rises a cylindrical metal sleeve 14 preferab y of nickel, coated on the exterior with an electron emitting coating, such'as the oxides of the alkaline earth metals, and'having a refractory metal filament 15 dis osed interiorly thereof. The construction 0 this form of cathode is more men, usmnoa r0 wmrnm 1 6. The modification of the invention shown fully described in a co-pending application of Marden and Lederer, Serial N 0. 292,116, filed July 12, 1928 and entitled Electron discharge device with indirectly heated cathode.

The cylindrical metal sleeve 14 is supported between two s aced disc shaped insulators 16 each of which has a centrally disposed boss 17 extending into the sleeve 14. Current conducting leads 18 pro'ect through the insulatin member 16- an are secured to the ends 0 the heating element 15. An enlargement is formed on each of the conductors 18, as by flattening thereof, which engages against the exterior face of the insulator to prevent separation of the insulators. The tensionof thecoiled filament element 15 is suflicient to maintain the insulators on the sleeve 14 in fixed relative position.

he control electrode 11 consists of a pair supporting wires having grid wires wound helically therearound and secured thereto. The supporting wires 20 are disposed in aperturesin the insulator 16 and support the control electrode in concentric relation to the cathode.

It should be noted that the cathode 14, the heating element 15, control electrode 11 and the insulating members 16 form a unit of construction which may be assembled separately from theremaining elements of the The screen grid or shielding electrode 13 consists of a box like structure of suitable mesh material, such as nickel mesh, having the lower end open and the upper end provided with a partition 21 having a U shaped or semi-cylindrical recess 22. The screen grid is supported upon the stem 23 of the tube by support wires 24 welded to the sides thereof and connected to the wires 25 whlch are sealed in the press 26.

The anode consists of a semi-cylindrical plate having a depending flange 27 by which it 1s supported from the'press, by the wires 28.

The construction is articularly suitable to accurate mounting, t e various parts being capable of being supported in proper positionwhile being assembled by ]1gS.

In assembling the elements upon the stem the plate 12 is temporarily supported by a jig from the heater leads 29 and welded to the support wires 28 the 1g is removed and the screen grid applied over the plate and held in proper spaced relation to the anode by a jig fitting on the wires 29. The support wires 24 of the screen grid electrode are then welded to the wires 25, after which the grid and cathode assembly, which was separately formed, is placed withinthe U shaped recess 22 and the current conducting leads 18 thereof welded to the support wires 29.

The current conductor 30for the grid may be sealed through the dome of the bulb, which is not shown, while the leading-in conductors for the cathode, screen grid, heating element and the anode are all sealed through the press 26.

With this construction the input circuit, that is, the control electrode and lead 30 is completely shielded from the out-put circuit, including the plate and the plate lead 28, by the screen grid 13 and capacity effects therebetween are substantially eliminated.

The screen grid should extend well down around the press so as to prevent capacity effects between the plate leads and the lead 30 of the control electrode. To enable this to be accomplished conveniently an opening 31 is provided in the opposite side 32 of the screen grid, to accommodate the support wires 29. This is preferably accomplished by cutting and bending a portion 33 of the mesh upwardly over a strip of metal .34, the object of this construction being to prevent a reduction in the total quantity of metal at the center of the-sides 32 so that the screen grid may be heated, inductively by high frequency currents without unduly'heating the portion immediately above the recess 31. If desired the screen grid, with the exception of the partition 21, may be made of fine mesh or of a solid material. The partition plate 21 may be made of coarser mesh so as not to restrict the electron fiow unduly between the cathode and anode.

In Figures 4 and 5 a modified construction is shown, which differs from the structure of Figs. 1 to 3 in the unitary control electrode and cathode assembly.

In Figure 4 the assembly consists of the cylindrical or tubular cathode 35, which is carried b the insulating discs 36, as in Figure 1. he control electrode comprises a single support wire 37 having a grid wire wound therearound, one end 38 of said support wire extending through an aperture in the insulating disc 36 and the opposite end being sup orted from a glass bead 39 by a wire 40. he glass bead 1s sup orted above the cathode by supports 41 an is provided with horizontally extending wires 42 which may be welded to the screen grid support wires 43.

This unitary control electrode and cathode structure, comprising the bead 39, the control .electrode and the cathode may be assembled separately, and applied to tlK mount, as with the construction of Figure 1 the supports 41 being welded to the supports 42 and the conductors for the heating elemem of the cathode being welded to the conductors 44.

Figure 5 shows a unitary grid and cathod structure similar to that of Figure 4 but em ploying a filamentary cathode 45. The con trol electrode 46 is wound upon a suppor 47 slidingly en aging in an eyr let 48 depend ing from the g ass bead 49.

In both the constructions in Figures 4 am 5 expansion of the control electrode is per mitted by the sliding engagement of the sup port wire 37 or 47 in the aperture in the dis 36 or eyelet 48, res ctively.

In Figures 6 and an inverted constructioi is shown in which the partition 50 of th screen grid is arched over the press, the an ode 51 being disposed above the partitio1 and the control electrode and cathode assem bly being disposed beneath the partitior The anode 51 is supported from a glass bea 52 carried by the support wires 53 of th screen grid 54. The leading-in conducto 55 for the anode is taken out through th dome of the bulb. The tubular cathode 5 and contained heater element is mounted be tween two spaced insulators 57 carried fror the press of the tube, by support wires 5 which also serve as current conductors to the hcatin" element.

The co.-.crol electrode comprises a heli of line wire I} wound about support wire 6 which is also supported from the press.

In all of the constructions shown it will 15 noted that the screen grid substantially S111 rounds both the anode and the control elet trode and the leading-in conductors therefo one of said elements being disposed on or side of the transverse partition screen an the other of said elements being disposed o the opposite side thereof, so that efl'ectii and complete screening of the control elei trode and anode is obtained.

It is usually preferable to mount a scree grid tube in a suitable shielded box-lil structure to separate theinput from the on iut. Such shield should be so arranged that be outside shield merely forms an extension f the screen grid inside the tube.

The construction is relatively simple, inolving few parts and may be readily assemled as a factory operation.

It is obvious that many changes may be lade in the construction shown and described ithout departing from the invention and I not desire to be limited to the specific deiils shown, except in accordance with the ppended claims.

What is claimed is: 1. An electron discharge mount comprislg a cathode, control electrode, anode and a nelding electrode said shielding electrode imprising a box-1i e structure partially suriunding said other electrodes and a partion having a U-shaped recess extendin 'ansversely of said shielding electrode, 'sai antrol electrode and cathode being disposed L said recess on one side of said partition and id anode being. disposed on the opposite do of said partition. 2. An electron discharge mount comprisg a cathode, control electrode, anode and a uelding electrode," said shielding electrode mprising a box-like structure partially surunding said other electrodes said shielding ectrode having a closed top of grid strucre provided with a recess, said control elecodeand cathode being disposed within said cess and said anode eing disposed within id shielding electrode. 3. An electron discharge mount comprisg a cathode a control electrode, an anode 'rizontally' disposed therein, a screen grid, least partially surroundin said other :ctrodes, and a partition in said screen grid ving a substantially semi-cylindrical re- ;s, said control electrode being disposed thin said recess and said anode bein dissed on the opposite side of said partition. 1. An electron discharge mount comprisa cathode and a control electrode therein nmon insulating means supporting said :hode and control electrode, an anode suprted independentl Y of said cathode and itrol electrode an a screen grid partially rounding the other electrodes, said screen ,d having a partition partially encirclin (1 control electrode and cathode and said )de being disposed on the opposite side of d partition remote from the control eleccllle, and being substantially parallel there- B. An electron discharge mount comprisa tubular cathode therein, a heating elent disposed within said cathode, insulating mbers at each end of said cathode serving iupport the same, a control electrode, sup- -ted from said insulating members, an

Ide partially encircling said control elecde and a screen grid interposed between i anode and control electrode, said grid having a portion at least ing the other electrodes.

6. An electron discharge mount comprising a hollow tubular cathode therein, insulating members extending across the ends of said cathode, a control electrode surrounding said cathode and supported between said insulating members, an anode at least partially surrounding said control electrode, a screen id of box-like shape substantially surroun ing said anode electrode, said grid having a U- shaped recess concentric with said control electrode and interposed between said anode and control electrode.

- In testimony whereof, I have hereunto subscribed my name this 27th day of December,

ERNEST ANTON LEDERER.

partially surround- 

